Sheldon Janet Plankton, preferrably just Plankton, is a very small sea plankton who usually finds himself on the wrong end of his plans being spoiled by Mr. Krabs. His computer w.i.f.e, Karen, will usually attempt to assist him but he rarely listens. He once pulled together an entire family of Planktons to steal the formula. That, obviously did not work out so well.

He is the kind of person who would lie to get anything, for example, he tried to lie about having a friendship with SpongeBob just to get the formula. He did the same thing with Mr. Krabs once as well. But that dragged out longer.

In episodes he has a big part in, you can always expect him to either lie to somebody, fail at another Krabby Patty theft attempt, or be very sarcastic. In fact, he is probably the most sarcastic character on the show except from Squidward. He is also made up of 1% evil and 99% hot gas.